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Naval Medical Research Institute
This is an abstract for a talk to be given at the Fifth Foresight Conference on Molecular Nanotechnology.
Large biological systems represent a challenge to cryobiologists because
of their diverse cell populations, the inability to apply high cooling and
warming rates, and the requirement for preservation not only of cells but also
of extracellular connective tissue and cell-matrix and cell-cell connections.
Examples of complex biological systems that tolerate massive distortion by ice
exist, and even some mammalian organs have survived and functioned after
extensive ice formation, but the general experience and concensus is that the
best option for the cryopreservation of large systems is generally metastable or
quasi-stable vitrification as introduced by Fahy in the early 1980's. With
increasing size, vitrification becomes increasingly difficult on statistical
grounds, but the volume fraction of the sample that undergoes injury from random
heterogeneous nucleation may be small. Both the problem of rare nucleation
events during cooling and the problem of devitrification on warming can be
approached by the design of solutions that maximize biological viability but
minimize ice crystal nucleation and ice crystal growth. Molecular design
techniques can play a role in addressing these issues. As of this writing, it
is probably possible to vitrify rabbit kidneys with preservation of viability in
the vitrified state, but we do not yet have the technology to restore these
kidneys to active function. However, in the future, it should be possible to
warm these kidneys sufficiently quickly to demonstrate viability.
Gregory M. Fahy, Ph.D., Organ, Inc., c/o Naval Medical Research Institute, Building 29, Bethesda, MD 20889, email: 72124.1173@CompuServe.COM
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